The invention relates to an ignition system.
The use of alternating current for separate ignition in internal combustion engines is known. The use of alternating current for ignition has the advantage that the spark discharge at the spark plug can be maintained for any length of time so that the engine requirement at any point in time can easily be matched, increasing the efficiency of the internal combustion engine through more complete utilization of the fuel mixture and reducing the pollutants in the exhaust. DE-OS 1 539 183 shows an ignition system with a primary and secondary circuit of a step-up transformer, whose primary circuit is designed as a parallel and series resonance circuit. This resonance circuit, following a rapid discharge in the secondary circuit, generates an alternating current at the spark plug cathodes In addition, DE-OS 25 17 940 teaches a capacitor ignition system for internal combustion engines with ferromagnetic resonance in which a second control circuit generates an oscillating current in the primary and secondary windings only after each discharge of the primary capacitor, allowing an alternating current to flow for a predetermined period of time at the spark plug.
Another alternating current ignition system is described in DE-OS 29 34 573. In this ignition system, an oscillator circuit controls a transistor feedback circuit connected to the primary winding of an ignition coil. This oscillator circuit is controlled by the switch positions of the breaker contacts of an ignition distributor and generates an alternating current signal with constant frequency at the spark plugs.
One disadvantage of this known ignition system is that generating the alternating current signal assumes an input signal triggered by a starting pulse, necessitating additional circuit elements to generate the starting pulse.
Another disadvantage of these known ignition systems is that the energy supply is provided over a constant ignition interval, thus generating an alternating current signal with constant power at the ignition contacts. If the secondary circuit is not satisfactorily closed, for example if the mixture fails to ignite, if the ignition contacts are short-circuited, or if the spark plug connector become disconnected, this can lead to excessive power being supplied, which can result in damage or even destruction of the electrical components of the ignition system.